In conventional fluid treatment systems, a fluid supply line is interrupted and fluid treatment elements such as filters are inserted into the fluid flow path. When the filtration system is initially installed the fluid flow is shut down, and the entire fluid system is taken out of service. This shutdown is inconvenient and time consuming. Additionally, new filter elements must be installed from time to time when the filter becomes overly contaminated and the effectiveness depreciates below an acceptable level.
Filter cartridges were created to make replacement easy. These cartridge systems sometimes make provision to isolate the fluid treatment system from the fluid utilization system and avoid excessive interruption of the fluid flow when filter elements are changed. For a period of time during which the filters are being changed, unfiltered fluid flows through the system served.
In order to minimize the time and effort required to replace filter cartridges in a filtration system, filters have been provided with quick-connect couplings. Quick connect and disconnect fittings have been employed to permit a single device to be coupled at different locations. This permits the device to be used at several work stations without permanently attaching a device at each outlet.
A filter system which uses quick-connect couplings is shown in Hiller, U.S. Pat. No. 3,950,251. Hiller discloses a horizontal mounting filter cartridge which allows the cartridge to be replaced without any vertical displacement. This ability limits the access space required to replace the cartridges and minimizes the effort required. However, many shortfalls have been recognized in the quick-disconnect couplings shown in Hiller.
The Hiller system uses a single inlet/outlet port at the cartridge's top. This single connection coupling allows an easy mounting with a cost effective mounting coupler. Fluid flows into the Hiller coupler, down a porous plastic tube, through the activated charcoal element and back through the coupler's outlet port.
However, since the amount of filtration effectiveness is directly proportional to the activated charcoal surface area with which the fluid interacts, and the amount of time the fluid remains in contact with the charcoal surface area, the Hiller filter produces an uneven fluid filtration and uneven contact time. The fluid flowing through the charcoal at the bottom of the filter (distant the ports) is cleaner than the fluid flowing through the charcoal at the top of the filter (proximate the ports). Additionally, this cartridge filtration system deteriorates extremely rapidly and wears out unevenly because the charcoal proximate the cartridge ports has a greater fluid flow rate than the charcoal distant the ports.
The Hiller cartridge single adaptation port also uses the water pressure itself to flow past the activated charcoal and against gravity to retain the outlet port.
Furthermore, the Hiller cartridge system is unstable. By using the Hiller coupler system in order to allow cartridge filter installation, the filter is limited to a single anchoring placement. Any jarring of the filter places the entire jarring force on the single anchoring at the coupler ports, making the filter extremely susceptible to cracking and leaking.
In conventional filter systems the fluid flow bypass can also lead to problems. Usually the replacement period is a relatively short interval and need not be the source of any major problems. However, most bypass systems include a first valve or set of valves which exclude fluid from the bypass line and direct all of the fluid through the treatment device. A second valve or set of valves switches fluid supply to the utilization system alternatively from the bypass line or the treatment device.
Depending upon the size of the bypass, a finite volume of fluid can be trapped within the bypass line during filtration. Over the long period of time between changes of treatment elements, such as filter cartridges, such fluid trapped in the bypass can stagnate, permit the growth of bacteria, and absorb foreign materials from the piping itself.
Most installations ignore this contaminated fluid. This may be acceptable in large systems where the usage of fluid is so great that the incremental volume of stagnant water poses little or no threat to the integrity of the system, but it is never desirable. The contaminated fluid becomes a substantial problem in special purpose treatment systems such as water filtration systems of the type used in beverage dispensing systems, ice makers, vending machines, and other installations where the quality of even small quantities of fluid is important or where health and safety considerations are involved.